The invention relates to a device and a method for detecting attempts at fraud on an apparatus for reading and writing on a chip card for example a smart card.
Such devices are advantageously used in service systems--for example in automatic-payment phone units (payphones)--which operate with electronic chip cards.
In an attempted fraud situation, use is made of an altered chip card or a card which is externally similar thereto, with connecting points arranged in the same way, at least one of the connecting points being connected to an electrical feed line of a unit which is present outside the writing and reading apparatus and which is used to carry out the attempted fraud. The attempt at fraud can be detected by checking whether there is an inadmissible feed line of that kind.
A device is known (EP 0 468 848 A1) in which a signal in a feed line, if such is present, of a card receiver, can be detected by means of an inductive sensor and selected filter which is connected on the output side thereof, use being made of the fact that in the reading and writing operations a chip card is processed by signals at a known standardized frequency.
It is also known to a transmitter in the card receiver at one end of the chip card and a receiver at the other end thereof, and to use a feed line, if such is present, as a transmission medium, coupling occurring galvanically at the transmission end while at the receiving end coupling is effected inductively (EP 0323 347 A1, FR 2 554 262, FR 2 646 260) or capacitively (FR 2 646 260), or coupling occurring at the transmission end inductively and at the receiving end inductively (EP 0 447 686) or galvanically (EP 0 454 570).
Also known is a device having an oscillator (FR 2 646 261) which has a frequency-determining element which is moved over the chip card so that the feed line, if present, causes a disturbance at the output of the oscillator.
In the known devices, mechanical devices such as for example antennae or movable sensors are to be arranged in the card receiver in the region of the chip card in such a way that they are substantially protected from damage.
The invention is based on the problem of providing a reliable and well-protected device for certainly detecting attempts at fraud on an apparatus for reading and writing on a chip card.